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2001 Dodge Ram All Even Misfire Codes! P0300, P0302, P030

Tiny
DEREKSAFLEY
  • MEMBER
  • 2001 DODGE RAM
  • V8
  • 4WD
  • AUTOMATIC
  • 160,000 MILES
Hello! My check engine light came on and the shop said it was a misfire. I replaced the plugs, wires, dist. Cap, rotor and had the compression checked, all within normal levels. I checked the codes again when the check engine light came on again and it lists all my right side cylinders as misfires! It does idle a bit rough at times so I do believe it misfires occasionaly. If my compression is good, all new wires, etc. Why would exactly and only the EVEN cylinders misfire? Seems strange. I know it's an high milage vehicle but I want to maintain and repair it rather than buy new. Something strange that may or not be related, I recently replaced my climate control blower resistor and noticed that the wires around the plug were very brittle and had developed some had cracks around the wire coating. Probably made worse by me bending the wires when I removed the old and installed the new resistor. The wire bundle to the resistor now needs to be jostled occasionally to make the blower work in all four speeds. I am in the process of fixing this, but couldn't help but notice that the check engine light comes on almost every time the blower motor resistor wires are jostled. May not be related, but though better bring it up now than later if it is important.
Thanks in advance!
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Saturday, January 3rd, 2009 AT 7:56 PM

12 Replies

Tiny
BUDDYCRAIGG
  • MECHANIC
  • 2,262 POSTS
This is my best guess as what to check out.

All of the injectors plus the coil all get their power from the same circuit. So i'll assume that the positive feed to the right bank is ok.

All 8 of the injectors have their own separate ground wires.
Are the ground wires ran through a harness next to the blower motor wires?
Could the blower motor wires have melted the injector ground wires?

Is the connector for the right bank clean and secure?
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Saturday, January 3rd, 2009 AT 9:06 PM
Tiny
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Hello.
Thanks for the response. Update.
I cleared the error codes and reset the check engine light. I ran the truck and after a few miles the check engine light came back on. I checked and sure enough, again, the even cylinders are showing misfires. Still nothing for the odd cylinders so yes, I think the coil is ok.
In response to your comments, the blower motor resistor wiring is inside the truck cab under the passenger side dash. I think all the fuel injector wiring is inside the engine compartment. I dont think they ever come in close proximity. I will check the fuel injector grounds, test the resistance of each injector and the votage of each connector and get back to you with my results. Great suggestions!
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Saturday, January 3rd, 2009 AT 10:22 PM
Tiny
BUDDYCRAIGG
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I looked again, and there doesn't seem to be any connectors between the injectors and the control module on the fire wall.

What about fuel delivery?
How is the plumping between the left and right banks?
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Saturday, January 3rd, 2009 AT 10:38 PM
Tiny
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Update.
For some reason if I leave my climate control OFF no codes appear. As soon as I turn it on, all 4 cylinders on the passenger side show misfires! How strange! Any ideas?
Thanks!
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Monday, January 5th, 2009 AT 6:04 PM
Tiny
BUDDYCRAIGG
  • MECHANIC
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That is odd.
I looked at the heater controls and I didn't see anything that could have to do with it.

I dont know what it would prove, but could you unplug the blower motor and see what happens.

The blower always has power when the key is on, and it's grounded through the resistors and dash switch.
I'm curious to see if completing the ground circuit will cause the missfires.
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Monday, January 5th, 2009 AT 6:54 PM
Tiny
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Hey! I read on another forum that a guy had a similar problem that was traced back to his ac compresor malfunctioning. I know that when my temperature knob is turned into the mid or cool zone that my ac compressor kicks in sporadically. Have you ever heard of this?
Thanks!
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Monday, January 5th, 2009 AT 9:12 PM
Tiny
BUDDYCRAIGG
  • MECHANIC
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No, i've never heard of that.
But unlike Dr. Phil, I don't know everything.
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Monday, January 5th, 2009 AT 9:15 PM
Tiny
DEREKSAFLEY
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Hello.
So I have been driving with no climate controls turned on to see if the pattern stays the same, I have been thinking the CEL light and right bank of cylinder misfire codes have something to do with my climate controls. So no heat, no air, no cool, no fan. Then my CEL light comes on and I say "oh well, scrap that idea" and turn on the fan and suddenly the CEL light goes off! How weird is that! Any ideas on where to start looking? Thanks!
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Wednesday, January 7th, 2009 AT 1:16 PM
Tiny
BUDDYCRAIGG
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https://www.2carpros.com/articles/mitchell1eautorepair-car-repair-manuals

I can't find a diagram of how your fuel plumbing is layed out. could you explain it to me or take a pic?
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Wednesday, January 7th, 2009 AT 2:22 PM
Tiny
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It has two rails (one on each side) which the fuel injectors draw from. Ealier I thought this might be why only the one side is showing misfires until the whole climate control connection became more frequent.
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Wednesday, January 7th, 2009 AT 7:52 PM
Tiny
BUDDYCRAIGG
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I meant like
the left side is supplied first from the fuel pump and then the right side is connected with a hose.
And then the fuel pressure regulator is on the end of the right rail, and then the return line
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Wednesday, January 7th, 2009 AT 8:13 PM
Tiny
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I ended up replacing the blower motor resistor and got a new battery and the CEL hasn't come on since.
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Wednesday, September 2nd, 2009 AT 1:13 PM

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